This invention is in the field of the use of functions of nuclear receptors in organisms. Nuclear receptors have a wide range of function, but their most conspicuous role is to enable cells to respond to hormones, such as estradiol, cortisol, and progesterone. Via the nuclear receptors the hormones influence gene transcription in cells, whereby the cells can change their function. Furthermore, it is known that the activation of gene transcription by nuclear receptors is facilitated or even enabled by coactivators. Several such coactivators are known. For example, Nishikawa et al (Toxicol. Appl. Pharmacol. 154, pp 76-83, 1999) describe screening methods for chemicals with hormonal activities using the interaction of nuclear hormone receptors with a coactivator. Their method is based on the finding that the interaction between the coactivator and a nuclear receptor, which is responsive to that particular coactivator, can be stabilised by a ligand that binds to the nuclear receptor. Such assays are also important in order to unravel the action of hormones and mechanisms for control of transcription of genes in general. With these techniques new medicines can be developed in order to specifically influence physiological processes related to the functioning of nuclear receptors for therapeutic, diagnostic, cosmetic and contraceptive purposes.